1. Field of the Invention
The present invention relates generally to a non-contact IC card wherein a semiconductor memory device is used as an IC chip. More specifically, the invention relates to the structure of an antenna coil which is formed in a non-contact IC card. The present invention is used for, e.g., a credit card or a commodity tag.
2. Related Background Art
FIG. 9 is a plan view of a conventional non-contact IC card, and FIG. 10 is a sectional view of the non-contact IC card taken along line A-Axe2x80x2 of FIG. 9. A quadrangular insulating substrate 1 to be an IC card substrate is made of a synthetic resin, such as a polyimide resin or an epoxy resin. The shape of the insulating substrate 1 is like a card about 5.5 by about 8.5 millimeters. An elliptical antenna coil 2 of copper or aluminum is bonded to the central portion of the major surface of the insulating substrate 1 by means of an adhesive 6. An IC chip 4 is formed at a suitable position outside of the antenna coil 2. The IC chip 4 is arranged above IC chip connecting terminals 8 and 8xe2x80x2, which are formed on one end and the other end of the antenna coil 2, to be connected to the insulating substrate 1 by means of an adhesive 5, such as a non conductive paste (NCP) or an anisotropic conductive adhesive. As shown in this figure, a bump 9 and the IC chip connecting terminals 8 and 8xe2x80x2, which are arranged between the IC chip 4 and the insulating substrate 1, are surrounded by the anisotropic conductive adhesive 5. The IC chip 4 is formed with the bump 9 on a connecting electrode (not shown), such as an aluminum pad. The bump 9 is bonded to the IC chip connecting terminals 8 and 8xe2x80x2.
Since the IC chip connecting terminals 8 and 8xe2x80x2 formed on both ends of the antenna coil 2 are close to each other to be connected to the IC chip 4, one end of the antenna coil 2 and a coil conductor close thereto must be beyond the same conductor to be close to the other end. Therefore, in order to prevent contact with each other, the antenna coil 2 is connected to a reverse conductor 7. The reverse conductor 7 electrically connects they one end of the antenna coil 2 and the coil conductor, which is close thereto, with the coil conductor of other portions by a connecting wiring which is embedded in two through holes (not shown) formed in the insulating substrate 1.
At present, in a non-contact card for use in a telephone card or a commutation ticket, a conductor serving as an antenna coil is formed on the major surface thereof. This conductor has uniform thickness at any positions on the insulating substrate which is an IC card substrate. Since the conductor is formed by etching a metal foil, such as a copper foil, sputtering or applying a conductive paste, any portions are usually uniformly formed. In a non-contact IC card wherein information is transmitted in a non-contact form, one of means for extending the communication range from a reader/writer is to reduce the electrical resistance of the antenna coil. Since the electrical resistance of the conductor is inversely in proportion to the sectional area thereof, the antenna coil portion of the non-contact IC card must be particularly wide and thick.
On the other hand, in a technique for mounting a semiconductor device using an anisotropic conductive adhesive or the like, it has been reported that the reliability of the connecting portion is enhanced as the distance between a semiconductor device (IC) and a substrate, on which the semiconductor device is mounted, is decreased (see Journal Of Circuit Mounting Society Vol.12, No.7 (1997), P.473, xe2x80x9cPair Chip Mounting By Anisotropic Conductive Adhesive Filmxe2x80x9d). It was revealed from this report that a flip chip mounting structure using an Au wire bump and an anisotropic conductive adhesive film can sufficiently temperature cycle resistance by controlling the height of connection. Furthermore, it was confirmed that the even in reliability test in HiPM, even after 500 cycles of tests, the connection is held, so that there is no problem in quality.
In order to decrease the distance between the substrate and the semiconductor device, it is considered that the height of the Au bump previously formed on the semiconductor element (IC chip) is decreased. However, if the conductor is made of a soft material, such as Al foil or Ag paste, the bump is embedded into the conductor, so that the distance between the substrate and the IC chip can not be controlled by using the Au bump. For that reason, it is required to control the distance between the substrate and the IC chip by decreasing the conductor thickness. In view of the foregoing, with respect to the conductor thickness of the non-contact IC card, there is a problem in that it is required to thicken the antenna coil to decrease the electrical resistance in order to maintain communication characteristics although it is desired that the thickness of the connecting terminal of the IC chip is decreased in order to improve the mounting reliability.
In addition, the non-contact IC card is particularly used for an IC telephone card or the like. In such a use, the non-contact IC card must have, e.g., a structure which withstands mechanical strength while maintaining the elasticity of the card so as not to be broken when the card is put in a trouser pocket to be under the hip. However, in general, it is very difficult for such a card to maintain a high mechanical strength.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a non-contact IC card capable of enhancing the connection reliability of an IC chip mounting portion, maintaining communication characteristics, and maintaining a high mechanical strength, and a communication system using the same.
In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, a non-contact IC card comprises: a substantially rectangular insulating substrate; a semiconductor chip mounted on a first face of the insulating substrate; and an antenna coil for transmitting information and for enhancing the mechanical strength of the insulating substrate, the antenna coil being arranged on the first face of the insulating substrate along the outer periphery of the first face, and the antenna coil having first and second connecting terminals which are connected to the semiconductor chip.
According to another aspect of the present invention, an IC card communication system comprises a non-contact IC card and a reader/writer, the non-contact IC card comprising: a substantially rectangular insulating substrate; a semiconductor chip mounted on a first face of the insulating substrate; and an antenna coil for transmitting information and for enhancing the mechanical strength of the insulating substrate, the antenna coil being arranged on the first face of the insulating substrate along the outer periphery of the first face, and the antenna coil having first and second connecting terminals which are connected to the semiconductor chip, and the non-contact IC card transmitting signals from and to the reader/writer via the antenna coil by the electromagnetic induction.